The great bulk of the digested food material is absorbed from the small intestine, and there are two pathways open through which the absorbed material can gain access to the blood. The one path leads directly to the liver, and substances taking this course are exposed to the action of this organ, before they enter into the general circulation. The other path is through the lacteal or lymphatic system, and constitutes a roundabout way for substances to enter the blood stream, since they must first pass through the thoracic duct before entering the main circulation. As a general truth, it may be stated that fats are absorbed through the latter channel, while carbohydrates and proteids follow the first path. The innumerable blood capillaries in the villi of the intestine take up the products resulting from the digestion of proteids and carbohydrates, through which they are passed into the portal vein, and thereby distributed throughout the liver. This means that both carbohydrates and proteids--or their decomposition products--are exposed to a variety of possible changes in this large glandular organ, before they can enter into the tissues of the body. As we have seen, practically all carbohydrate food is converted into a monosaccharide, principally dextrose, in the alimentary tract; and it is in this form of a simple sugar that the carbohydrate passes into the blood. This might easily mean a pound of sugar absorbed during the twenty-four hours, and would obviously give to the blood a high degree of concentration, unless the excess was quickly disposed of. Sugar is very diffusible, and if it accumulates to any extent in the blood it is quickly gotten rid of by excretion through the kidneys. This, however, is wasteful, physiologically and otherwise, and does not ordinarily occur except in diseased conditions. Further, physiologists have learned that a certain small, but definite, amount of sugar in the blood is a necessary requirement in nutrition, and it is the function of the liver to maintain the proper carbohydrate level.